An actual thing that happened when my parents were in college: an enterprising student started an anonymous service where, for a price, you could pay to have a professor pied by a streaker. (I get the impression that streakers were the 70s equivalent of planking . . .) Administration took a lot of time trying to track down the "don" of the pie mafia. Dad found out much later that it was a friend of his who was a divinity student at the time

A Scenario where the Student Council holds a Talent Competition and has to screen out bad acts and provide some form of security for the event so someone doesn't sabotage the event either before or during someone's performance.

There's also student publications. Allowing them to write and publish whatever they want will undoubtedly drag down the school's reputation but squeezing too tight on censorship will destroy your Council's Karma. You could also get into a power struggle with student publications.

I think you could also incorporate both
1) council member loyalty missions where instead of earning or losing Karma and Reputation, you could gain or lose loyalty with one of your council members
2) Non-plot essential mission arcs. I think the best way to describe this as consecutive related cases: Like the plot missions, there is continuity between them, but they aren't related to the larger stories. Some of the characters between the cases will be the same, some of the locations may be the same. I think this in particular would allow for playthroughs to feel drastically different from each other and provide more mission variety.

Piggy backing off of 4Dam-Ghost-Nappa a bit and inspired by reading Mallory's picnic conversation just now (and promising her more events later in the year that never quite materialize), I would like to see a few cases that are more like council-sponsored activities than straight up mysteries. We have the lemonade stand, but I would like to see things that are less like the various event guarding missions and more proactive. Maybe you could send a girl out to help organize fundraising for a school dance, hold a secret santa-like event where you have to screen the in-coming presents for pranks, or have a booth at a school or town fair.

Managed to sell enough Steam copies so far that I am at least thinking about case additions!

I'd also like to find more uses for some of the location cards that don't come up as often. Obvious boarding school stories tend to lead to an over-reliance on classrooms and bedrooms. Currently plotting more things to do in the library.

Rumors of a Food Fight going to break out in the Cafeteria.
Stolen Gym Clothes was something that happened to me personally and drove me up a wall because it meant I had to sit there and look stupid for 40 minutes and because a lot of guys in the locker room laughed behind my back.

"Senior Pranks" were so called at my high school because senior students would sometimes do things as a "So long, suckers!" rite of passage. Common examples involved clogging toilets with unusual implements, TPing an empty room, minor vandalization, tricking substitute teachers by "switching names" in class.

Regardless of what happens in the library, I believe that there should be some minor scene where you interact with a library assistant named Minnie, who was one of your rivals for Student Council President. What do you mean I'm salty about not being President in Magical Diary? Bonus Points if there are some books that Elsa can thumb through that refer to the mythical kingdom of Nova, speculation on the existence of secret magical societies in post-Harry Potter literature, etc.

My own student council was responsible for hosting its own events and fundraisers and I think Elsa herself could be given the choice to give speeches at events like before big sports games or something as a way of gaining Karma or undermining Talmage and/or the Red Mask Society. Bake sales, movie-themed parties (*cough* Vonne *cough*), Scavenger hunts, charity drives,and volunteer services are all ways to gain Karma/Reputation and the player could use them if they have sudden downtime (accidentally completed your missions too early) or as a way to earn back some good publicity in a pinch. You could make a "Host ..." option alongside the Supply Closet and the Training Room.

Items for a school performance (such as costumes) go missing, motives could include: jealousy of the girl who got the lead, wanting the costume or prop themselves, anger that one of the performers is neglecting their social relationships, and not wanting to be in the performance/inability to cope with the pressure

Huahuahua as an actual real life former Student Government President at an actual real life Boarding School that had to do actual Real Life Discipline let me tell you things that happen there that might be potential cases.

Disclaimer: I am not yet done with the game, so similar cases may exist and I just haven't seen them yet.
Other disclaimer: Most of these stories I present are real and I am continually getting school flashbacks when I play this game.

Dorm Wars. Perhaps too close to vandalism, but I'm not sure. A pair of roommates or a couple of different rooms might team up against other groups. In my experience, there are some great variations that might translate well. We've had people get into wars without their roommates knowing, leaving the innocent roommate to take the fallout. Some are just plain old fun, others were mean-spirited, and yes, there is great potential for scandal... my younger brother actually had all of his bedding dipped in heavy bleach, which probably would have caused sickness or injury if he hadn't realized soon.

Late night sneaking out sessions. Kind of a combo of secret society and the urgent missing girl plots, perhaps? I was directly dealing with a late night Hide and Seek club, a budding Ghosthunter society, and some lovebirds. I was told of kids who would try to run away, only to injure themselves with snakebites or falling off a cliff (we were in the middle of the woods with a lot of caves and drops nearby).

Election rigging. The SGA can't be the only elected student organization, right? The SGA may have to look out for other elections to determine if a landslide vote is rigged (on either side, as some people can't say no even if they want to!) or genuine. Perhaps someone's bribing their classmates to vote for them or promising dangerous favors? Or else, maybe a smear campaign uncovered dirt on a prominent student?

General entertainment pranks. Nothing MEANT to hurt anyone, but rather to make them laugh! More harmful to the staff than students... unless someone gets hurt doing them. I remember once someone managed to hoist ten mattresses up onto the roof of the girl's dorm at my school and everyone thought it was hilarious. Also, a mysterious figure doing parkour on the roofs of the education buildings had them (ok and me too a little) laughing. But there was potential for it to turn real dangerous real fast. On a similar vein, not my story but a friend who went to a different boarding school mentioned literally kidnapping a friend as a birthday prank by having all their friends pick up the girl's entire bed (she was a heavy sleeper) and moving it outdoors. Could have gotten bad real fast if the girl slept naked or something, perhaps.

Perhaps a bit racy, but the itches. As mentioned, my school was in the woods and we had these nasty mites outdoors. If you canoodled in the wrong places, everyone would know it cause your certain bits would be very, very itchy until you went to the infirmary. However, an itch issue could also come from falling in poison ivy, dry skin, dermatillomania (if you're just seeing cuts and scratches maybe) or perhaps a lice outbreak?

Of course, class skipping might also work. Girls might be habitual oversleepers (leading to why? is it drugs or alcohol or any sort of late night partying?), have an excuse for a club and just forgot to show the teacher, legitimately cutting class, or maybe something else?